[racket] tool to remove unused requires?

Is there a tool to remove unused "require" clauses from a Racket source 
file?

If Check Syntax doesn't think the clause is used, that's good enough for me.

(I recall someone answering this question, probably in 2010, and 
pointing to a tool, but I can't find the discussion in the mail archives.)

-- 
http://www.neilvandyke.org/